This invention relates generally to a rescue device for use in marine operations and more particularly to an apparatus and method for erecting a temporary emergency walkway for personnel between an offshore oil platform and a vessel. For the purposes of this disclosure, the term "oil platform" shall be understood to refer to any offshore structure used in connection with the exploration for or recovery of oil and/or natural gas.
In earlier years offshore activity was generally limited to relatively shallow and calm waters such as the Gulf of Mexico. As the demand for oil has increased, however, the trend has been to explore and drill in deeper and more dangerous waters. There has been much effort and investment made in the development of various tracts in the North Sea. In that area drilling has been conducted in water varying in depth between three and six hundred feet and production platforms are currently under construction in water of such depths.
The North Sea is a relatively rough body of water. In certain areas, the mean wave height is six feet or greater about 35% of the time. As a result, marine operations are frequently interrupted due to heavy seas. Oil drilling and production in an environment of this sort inherently involves greater risk for workers on the platforms than they might be exposed to in calmer, warmer oceans. If the crew of an offshore oil platform is forced to evacuate the platform because of an actual or impending disaster, they may be exposed to a very hostile ocean environment requiring special protection for survival. Most platforms are equipped with the conventional lifeboats and in some cases with rather sophisticated self-contained escape vessels which are completely enclosed and self-propelled. While conventional open life boats may provide a satisfactory means of escape in some situations, they may be totally inadequate in the North Sea. They are easily swamped or capsized in heavy seas and offer the crew little protection from exposure to such cold waters.
The more sophisticated escape vessels offer greater protection but they also may become unmanageable in bad weather. Due to their greater complexity, the probability of their malfunctioning is inherently greater. Also, when the possibility of a fire arises, or a fire actually occurs on a platform, one of the first safety measures taken is to shut off all power on the platform. If it subsequently becomes necessary thereafter to evacuate the crew, power will not be available to activate or launch an escape vessel. Under such circumstances, it may even be unsafe to start the engine of an escape vessel in the immediate vicinity of the platform.
In some instances, helicopters have been successfully used to rescue endangered personnel from oil platforms. If the platform is actually on fire, however, it may not be safe to approach it with a helicopter. Also, the relatively small passenger carrying capacity of most rescue helicopters makes it impractical to use them to evacuate large crews which will man the giant platforms which are under construction or planned for the future.
Accordingly, it can be seen then that under many circumstances the various escape devices presently known and used in connection with oil platforms may be of little or no use to an endangered crew in an environment such as the North Sea.
Also, it may be necessary after the platform has been abandoned and the fire, if any, has been extinguished to reboard the platform to cap the damaged wellheads. Under these circumstances, the danger of fire or explosion may still exist and the reboarding must be accomplished quickly and as safely as possible regardless of the existing weather conditions. If the seas are high, it may be difficult or impossible to board the platform from a conventional boat. Approaching in a helicopter may be unsafe due to the danger of another explosion.
Accordingly, it is an object of this invention to provide an apparatus and method for safely evacuating personnel from an offshore oil platform in heavy seas.
It is also an object of this invention to provide for an apparatus which can be used by personnel to safely and quickly reboard an abandoned, powerless platform in heavy seas after an explosion or fire thereon has been brought under control, and to provide the personnel with power from a service vessel.
It is a further object of this invention to provide an apparatus and method for quickly and safely evacuating relatively large crews from offshore platforms under weather conditions more severe than could be contended with by devices known in the prior art.